The present invention relates to a broadcast receiving system with a function of on-screen displaying channel information of receivable digital/analog broadcasts.
Conventionally, in the television broadcast, in addition to the image broadcast, there has been commercially applied a multi-teletext broadcast which is performed by multiplexing the multi-teletext broadcast during a period of the vertical retrace line for image signals. In the multi-teletext broadcast, it takes a time from the channel selection to the display of desired information, so that various devices have been made. By way of example, in the multi-teletext broadcast, there is a teletext broadcast receiver which displays the channel information stored in memory on the display device to permit the user to select a program he wants to see and hear, thereby allowing the user to select easily the program (for example, see Japanese Unexamined Patent Publication No. 64-7786). In the multi-teletext broadcast, there is also a teletext broadcast receiver which receives the teletext broadcast from a broadcasting station to store the received information on a memory, then automatically and sequentially select other stations to store the received information on the memory at predetermined time intervals, and to make sequentially the received information thus stored audiovisual, thereby reducing a time required to obtain the desired information (for example, see Japanese Unexamined Patent Publication No. 64-89871).
Meanwhile, in recent years, in addition to conventional analog broadcast, there are originated and rapidly popularized a BS (Broadcasting Satellite) digital broadcast capable of high-picture-quality and multi-channel broadcasting and a digital broadcast represented by the CS (Communications Satellite) digital broadcast. The digital broadcast, for example, in the broadcast according to the digital broadcasting standard ATSC (Advanced Television System Committee) of North America, is originated through a physical channel different from that for analog broadcast. Among these, there are many digital broadcasts originated from the same broadcasting station or the same system of broadcasting station as the prior art analog broadcasting station. In this case, in order to improve the operations of the users accustomed to these prior art channel numbers, the digital broadcast are administered so that the station can be selected and displayed through a virtual channel assigned the same channel numbers as the prior art analog broadcasting channel numbers.
In the digital broadcast, there have been assigned to each channel a carrier wave having a predetermined frequency band different from that for the analog broadcast. The channel is called a main channel, and one main channel includes a sub-channel to transmit one or a plurality of contents. The configuration of the sub-channels changes with a broadcasting time band, one of which is exemplified in FIG. 5 which shows a configuration of the sub-channels in a time band (8:00 PM to 12:00 PM) that has a main channel “4”.
In FIG. 5, in broadcasting, sub-channels of Nos. 0 to 4 are selected for 8:00 to 9:00 PM, sub-channels of Nos. 0 and 1 are selected for 9:00 to 10:00 PM, sub-channels of Nos. 0 to 4 are selected for 10:00 to 11:00 PM, and sub-channels of Nos. 0 to 3 are selected for 11:00 to 12:00 PM. Among these, the sub-channel of No. 0 (physical channel number of 4-0) involves analog broadcast according to the NTSC (National Television Systems Committee) Standard, while the sub-channels of Nos. 1 to 4 (virtual channels Nos. 4-1 through 4-4) involve digital broadcast. Also, a TV program broadcast through the channel “4-0” is a prior art analog-broadcast one, an SD (Standard Definition) program broadcast through the channels “4-1” through “4-4” are digital broadcast standard-picture-quality one, and an HD (High Definition) program broadcast through the channel “4-1” is a digital broadcast high-picture-quality one.
In the digital broadcast, the information (hereinafter described as the channel information) on the channel configuration fluctuating as described above is transmitted together with the signals of image and the like. Therefore, in the digital broadcast receiving system, by receiving the above-mentioned digital signals by the tuner, decoding them by the digital decoder, and analyzing the VCT (Virtual Channel Table) included in the decoded signals, the channel information of the broadcast is allowed to be obtained, and thus the channel information is stored in memory, and the stored channel information is OSD displayed from display means such as CRT. Then, referring to the channel information thus OSD displayed, the user can easily perform channel selection.
However, as described above, the channel configuration in the digital broadcast frequently fluctuates, so that even for the channel the user saw and heard before, a case where no channel has been broadcasted occurs (see FIG. 5). In a conventional system, a display corresponding to such fluctuating channel configuration has not been made, and particularly a channel whose sub-channel cannot be identified could not be displayed distinguishing from the channel of the analog broadcast or of the digital broadcast whose channel configuration can be identified. If the channel information obtained before is read from a memory to OSD display, even a channel the user cannot see and hear will be displayed at that point due to the fluctuation in the channel configuration, and on the contrary, a channel having become audiovisual will be not displayed, thereby all the more confusing the user.